Everything we have been told about the Olympic legacy turns out to be bunkum. The games are supposed to encourage us to play sport; they are meant to produce resounding economic benefits and help the poor. It's all untrue. As the evictions in London begin, a new report shows that the only certain Olympic legacy is a transfer of wealth from the poor to the rich.

Both Lord Coe and Tessa Jowell, the sports secretary, like the boosters for every city to have bid for the Olympics, have claimed that the games will lever us off our sofas and turn us into a nation of athletes. But Jowell knows this is nonsense. In 2002 her department published a report which found that "hosting events is not an effective, value-for-money method of achieving ... a sustained increase in mass participation". One study suggests that the Olympics might even reduce our physical activity: we stay indoors watching them on TV, rather than kicking a ball around outside. And this is before we consider the effects of draining the national lottery: Sport England will lose £100m.

The government's favourite thinktanks, Demos and the Institute for Public Policy Research, examined the claim that the Olympics produce a lasting economic boom. They found that "there is no guaranteed beneficial legacy from hosting an Olympic games ... and there is little evidence that past games have delivered benefits to those people and places most in need". Tessa Jowell must be aware of this as well - she wrote the forward to the report. A paper published by the London assembly last month found that "long-term unemployed and workless communities were largely unaffected [by better job prospects] by the staging of the games in each of the four previous host cities".

Far more damning is a study released last week by the Centre on Housing Rights and Evictions. In every city it examined, the Olympic games - accidentally or deliberately - have become a catalyst for mass evictions and impoverishment. Since the 1988 Olympics in Seoul, more than 2 million people have been driven from their homes to make way for the Olympics. The games have become a licence for land grabs.

The 1988 games are widely seen as a great success. But they were used by the military dictatorship (which had ceded power in 1987) as an opportunity to turn Seoul from a vernacular city owned by many people into a corporate city owned by the elite - 720,000 people were thrown out of their homes; people who tried to resist were beaten by thugs and imprisoned; tenants were evicted without notice and left to freeze (some survived by digging caves into a motorway embankment); street vendors were banned; homeless people, those with mental health problems, alcoholics and beggars were rounded up and put into a prison camp. The world saw nothing of this: just a glossy new city full of glossy new people.

Barcelona's Olympics, in 1992, are cited as a model to which all succeeding Olympic cities should aspire. But, though much less destructive than Seoul's, they were also used to cleanse the city. Roma communities were evicted and dispersed. The council produced a plan to "clean the streets of beggars, prostitutes, street sellers and swindlers" and "annoying passers-by". Some 400 poor and homeless people were subjected to "control and supervision". Between 1986 and 1992 house prices rose by 240% as the Olympic districts were gentrified, while the public housing stock fell by 76%. There was no consultation before the building began - the games were too urgent and important. Around 59,000 people were driven out of the city by rising prices.

Even before the 1996 Olympics, Atlanta was one of the most segregated cities in the US. But the games gave the clique of white developers who ran them the excuse to engineer a new ethnic cleansing programme. Without any democratic process they demolished large housing projects (whose inhabitants were mostly African-American) and replaced them with shiny middle-class homes; about 30,000 families were evicted. They issued "quality of life ordinances", which criminalised people who begged or slept rough. The police were given pre-printed arrest citations bearing the words "African-American, Male, Homeless": they just had to fill in the name, charge and date. In the year before the games they arrested 9,000 homeless people. Many were locked up without trial until the games were over; others were harassed until they left the city. By the time the athletes arrived, downtown Atlanta had been cleared for the white middle classes.

In 2002, there was much less persecution of the poor, but the economic legacy was still regressive: house prices in Sydney doubled between 1996 and 2003. No provision was made for social housing in the Olympic village, and there were mass evictions from boarding houses and rented homes, which the authorities did nothing to stop. The old pattern resumed in Athens, where the Olympics were used as an excuse to evict 2,700 Roma, even from places where no developments were planned.

In Beijing 1.25 million people have already been displaced to make way for the games, and another quarter of a million are due to be evicted. Like the people of Seoul, they have been threatened and beaten if they resist. Housing activists have been imprisoned. One man, Ye Guozhu, is currently serving four years for "disturbing social order", and has reportedly been suspended by his arms from the ceiling of his cell and tortured with electric batons. Beggars, vagrants and hawkers have been rounded up and sentenced to "re-education through labour". The authorities are planning to hospitalise mentally ill people so that visitors won't have to see them.

London is about to establish its credentials as a true Olympic city by evicting Gypsies and Travellers from Clays Lane in Newham and Waterden Crescent in Hackney: 430 people will be thrown out of the Clays Lane housing co-op and a 100-year-old allotment will be destroyed to make way for a concrete path that will be used for four weeks. Nine thousand new homes will be built for the games, but far more will be lost to the poor through booming prices, which are rising much faster around the Olympic site than elsewhere in London. The buy-to-let vultures have already landed.

The International Olympic Committee raises no objection to any of this. It lays down rigid criteria for cities hosting the games, but these do not include housing rights. How could they? City authorities want to run the games for two reasons: to enhance their prestige and to permit them to carry out schemes that would never otherwise be approved. Democratic processes can be truncated, compulsory purchase orders slapped down, homes and amenities cleared. The Olympic bulldozer clears all objections out of the way. There can be no debate, no exceptions, no modifications. Everything must go.

None of this is an argument against the Olympic games. It is an argument against moving them every four years. Let them stay in a city where the damage has already been done. And let it be anywhere but here.

· George Monbiot's book Heat: How to Stop the Planet Burning is now out in paperbackwww.monbiot.com